Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The invention relates in -the :Eirst place to a method
for suctioning submerged bottom material wi-th the aid
of at least a suction tube connected to a vessel, in
which the suction tuhe is lowered from the vessel in an
inclined ox vertical position, and a reduced pressure
or partial vacuum is created in the suction tuhe for
suctioning a mixture of bottom material and water
through the tube via one or more suction openings near
the lower side of the suction tuhe, wherehy eventually
the suction openings are graduallv lowered under the
bottom surface such that by suctioning the bottom
material, an excavation or trough is ~ormed in the
bottom. Such a method i5 clescribed in the article
"A suction dredger in sand pits" in "Civil ~nyineering
and Puhlic 1~10r~s Review", April 1970, Vol. 65, Mo. 765,
pages 403-405.
The major problem in this known method is to maintain
the suction opening(s~ at the most favourahle distance
from the vessel to the bottom material under swell and
wave conditionS. If the distance is too large then a
mixture of bottom material and a relatively large volume
of water is suctioned/ so that the transport concen-
tration decreases, whereas with too small a distance
the suction opening becomes clogged so that it is not
possible to suction any mixture of bottom material and
water. Therefore, complicaked swell compensators and
positioning systems are used in the known method to
maintain a constant distance hetween the suction opening(s)
and the bot-tom material. NotwithstandlncJ -these
measure~ it is not possible to use this method uncler
heavy wave conditions.
An object of the invention is to provide a method o~ the
type referred to ahove which is intenclecl to avoid the dis-
advantages referred to.
The invention provides a method for suctioning submeryed
bottom material from a suba~ueous environment with khe
aid of a suct,ion tube connected to a vessel, whereby the
suction tube is lowered from the vessel and completely
suhmerged in a downward extending position and suction
is created in the suction tube by suctioning a mixture of
hottom material and water through the tube by means of at
least one opening near the lower encl of the suction tube.
The lower portion of the suction tube is forced through
a certain depth into the bottom such that durin~ suctioning
of the mixture of bottom material and water always at least
a part of the weight of the suction tube is carried hy
a supporting surface formed in the bottom material, and
the suction tube is anchored at least in a direction
corresponding to the longitudinal axis of the suction
tube. A mixture of bottom material and water is suctioned
through the said at least one suction opening in the
suction tube near the lower end thereof at a distance
from said supporting surface, such that said at least
one suction opening i5 graclually lowered below the
surface of the bottom and, by suctioning -the bottom
material, an excavation or trouqh is Eormec1 in the bottomO
In this way the suction tube is in fac-t ~nchored in
the bottom, whereby an lncreasiny depth of this anchorage
results in an improved anchorage in transverse direction,
so that in khis anchored si-tuation the suction
openin~(s) can always he situated in the most favourahle
position for suctioning the bottom material, and only
a very simple swell compensator and eventually a
simplified positioning system is sufficient.
Because in the method accordin~ to the invention the
suction tube is ~supported by the bottom material the
vessel can also be supported by the bottom. Therefore
advantageously the vessel is suhmerged until below the
water level, because it is not necessary that the
vessel floats at a certain level under -the water
surface. In this way the vessel is for the most part
not influenced by water and wind so that the use of a
swell compensator is completely superfluous, whereas
the vessel with the suction tube can be suhmer~ed to
any favourahle suction depth. Furthermore, the created
underpressure can be us~d in an optimal way.
For the ~urpose of forcin~ the lower part of the suction
tube into the bottom or ~orcing said part urther downwards
a pressurized fluid can be sprayed throu~h openings
in or near the bottom or head side o e the suc-tion tul-e
into the bottom material.
In this way the consistency o:E the hottom material
underneath and around the supPorting surEace is broken
by the fluid jets and/or fluidized and suctioned up, so
that as a result of the :~orce exerted onto the hottom
through the suction pipe said pipe descends until the
pressurized fluid jets are lnterrupted, whereafter in
consistent types of soil again directly a supporting
surface is present, or the bottom material underrleath
the lower end of the suction tube is directl.y consolidated
and forms a supporting surface for the suction tuhe.
In relation with the spraying of a pressurized fluid or
separate therefrom a reduced pressure can be created
near the lower end of the lower part of the suction
tu~e, which underpressure is preferably derived from
the reduced pressure created in the suction tubeO
Because of the reduced pressure the bottom material in
the neighbourhood of the supporting surface is directly
suctioned away, causing the sucti.on tu~e to des~end
until the generation of the reduced pressure is stopped.
The invention, furthermore, relates to a system for
carrying out the method comprisinq a vessel and a thereto
connected suction tube having an open lower end, m~ans
for lowering the suction tube and means for creating
an underpressure in the suction tube, whereby according
to the invention underneath the open lower end of the
suction tube a supporting means is posi-tioned attached
to the suction tuhe and there is an open connection
between the open lower end of the suction tube and the
exterior of the suction -tube via one or more -transverse
passages.
Preferably the vessel can be em.hodied as an underneath
the water surface submergible vessel, such tha~ -the
suction tube supported by the aid of the supportin~
means on the bottom additionally supports the vessel.
In this way the suction tube can be emhodied as one
integral piece of tubing o:E predeter~ined length eliminating
the necessity of using an articulated or telescopin~
tube sections with hoisting cables as in the known
systems, necessary for bringing the suction openings
in the tube to a deeper leve].. Furthermore, the means
for ~enerating an underpressure can be ins-talled at an
optimal distance from the suction openinqs, because the
distance between the suction openings and the vessel is constant
and independent oE the suction depth.
The distance between the lower edge of the suction tube
and the supporting means can he adjustahle, wherehy
preferably the adjustment is realized in that a tube
section is slidable around or inside at least the
lower part of the suction tuhe and there are means ~o
extend or retract said tube section such that in the
extended situation a part of this tube section is positioned
:
outsid~ the suc~ion tuhe embodyin~ an elongation thereof.
In this way it is possible to suction th~ bo-ttom
material around and underneath the lower side o~ the
supporting means directly, so that the suction tllbe can
descend to a deeper level.
The suppoxting means can be connected to the suction
tube by the aid o~ elongated members, such as rods,
pipe segments or similar means such that the spaces
between the means form transverse openings or passages.
Preferably said ~ipe sections are forming therehy the
supply conduits for supplying a pressurized fluid to
one or more chambers, .~ormed into the supporting means,
whereby said chamber comprises openings for spraying
fluid ,ets into the hottom.
sy means of the fluid jets the bottom material around
said supporting means can hecome crumbled and/or
fluidized and can be suctioned off, so that the suction
tube can descend to a deeper level~
The suction tube can be embodied as a tube havin~ a
double wall, whereby the abovementioned pipe sec-tions
are with their upper ends insertecl into the annular
space between said walls.
It is also possihle that the supporting means i9 connected
to the suction tube with the aid of axially extending
wall parts such that the spaces between the wall par-ts
define the transversal openings.
Both walls of the suction tube in the embodiment in
which the tube has a double wall, extend in the axial
direction to reach the supporting means, whereby in
both extension walls opposed openings are made. Pre-
f~rahly, the bottom edges of these openings in the
inner extension wall are positione~ lower than the bottom
edges of the openin~s in tlle outer extension wall.
It is remarked that from the French patent 1,~3,~52
a method for suctioning submerged bottom material by
means of a suction tube is known 7 according to which
method the lower end of the suction tube is forced
over a certain distance into the hot-tom and a water
stream is created flowing from the exterior to the
interlor along and underneath the lower edge o the
suction tube, which water stream is not generated
continuously but intermitten-tly. The side wall of the
suction tube can have sideward directed openings, bu-t
the purpose of this is exclusively to create an additional
water stream for eroding the bottom matexial which is
in the form of a core present in the lower part of -the
suction tube for which reason the si(leward dir~cted
openings sho~ld be positioned as clos~ as possible to
the hottom edge.
The invention is no~ descri~ecl :in detail with
reference to the drawings in which emhodiments of the
invention are illustrated and with reference to which
the ~unctioning of the invention ~ith bottom material,
e.g. mainly consisting of sand, is explained.
~igures 1 and 2 show sc~ematically a first embodiment of the
suction tube according to the invention.
Figures 3 and 4 show schematically a second embodiment of the
suction tube according to the inventionO
Figure 5 illustrates schematically an embodiment of the whole
syætem according to the invention.
~'igures 6a-6f explain as example some successive steps during the
execution of the method~
Figure 7 illustrates on a larger ~cale an embodiment of the
suction tube.
Figure 8 æhows another embodiment of the suction tube.
~igure 9 ~hows cross-sections in the planes IXa, IXb and IXc in
fig. ~-
~igures 10 and 11 show a further embodiment of the suction tube,partly in longitudinal cross-section.
~igure 12 shows cross-sections through the planes XIIa,XIIb and
XIIc and XIId in fig.
Figure 13 illustrates a cross-~ection according to XIII in fig.
q
~s is shown in fi~. 1 an annular supportlrlg means 2 is
installed beneath the lower end o the sucti~n -tu~e or
pipe 1, which supporting means through rocls or pipe
sections 3 is connected to the suc-tion tube in a way,
not illustrated in detail, and the suction tube can be
moved upwards and downwards in relation to -the supporting
means. The supporting means 2 is alread~ forced in-to
the bottom 4, so that the supporting means and -there~ith
also the suction tube is carried by the supporting
surface 5. By generating a r~duced pressure or an
underpressure in the suction tube a mixture 6 of bottom
material, in general sand and ~ater, is suctioned
through the spaces between the pipe sections 3 to and
through the suction pipe.
After a certain amount of sand is suctioned in this way,
e.g. until a bottom profile 7 is reached it will be
necessary for further suctioning that the supportin~ means
is brought to a deeper level, for which purpose, as is
illustrated in fig. 2 r the suction pipe i9 brough-t closer
to the supporting means 2, so that near this supporting
means an underpressure or partial vacuum is crea-ted anæl
the bottom material in the neighbourhood of this means is
1uidized and suctioned off as is illustrated with 8 in
fig. 2, 50 that the supporting means with the suction
tube will descend to a lower level. ~fter removing
.. ..
L3
the underpressure near the supporting means 2 -the
suFporting means will consolid~te itsel~ onto the
surrounding bottom material, so that again a supFortincJ
surface is formed and the sucticning of bottom materia-
can proceed after t~e sucticn tube is raise~ agaln in
relation to the supporting means~
In the embodiment illustrated in fig. 3 and ~ the
suction tube comprises an outer tube 9 and an inner
tube 10 forming an annular chamber ]1 connected in the
not-illustrated upper sec-tion of the suction -tube with
a pressurized fluid supply means. The supporting means
12 is connected through an elongated wall part 13 of -the
outer tube 9 to the suction tube, whereas the supporting
means 12 comprises an annular chan~er 14 having
downwarcl directed no~zles 14', which chamber 1~ by
means of the pipe sections 15 is connected to the annular
chamber 11. In the wall 13 urthermore a number of
openings 16 are made through which openings 16 the
lower part of the suction -tube 9,10 communicates with
the exterior.
In fig. 3 the supporting means 12 is already forced into
the bottom 17 through a relatively large distance~ so
that the supporting means ancltherewith also the suction
tube is supported by the bottom resulting in a proper
anchorage in the hnrizontal cllrection. If an under-
pressure is generated in the suction tube, then a mixture
18 of sand and water is suc-tionecl through openincJs 16
to and through the suction pipe.
If after some time, ~.g. when the bottom profile 19 i~ r~a~hed,
the supporting means -12 should be brought to a deeper level~then
a pressurized fluid is supplied to the annular chamber 11, f~om
which s~id :fluid flows through the pipe section~ 15 into the
annular chamber 1~ of the supporting means 12, from which chamber
it is sprayed through the nozzle~ 14' into -the surrounding bottom
material a~ is illustrated in fi~. 4 by the arrows 20 and 21.
In this way the bottom mat~rial around the supporting means 12
is flui~i~ed as is illustrated at 22, and suctioned away thr~ugh
the suction pipe, so that the supporting means together with the
æuction pipe will descend to a lo~er level.
If the spraying of pressuri~ed fluid through the openings 14'
i9 thereaft~r stopped, then the ~upporting mean~ will co~solidate
itself onto ~he surrounding bottom material, 80 that again a
~upporting ~urface for the suction tube is formed.
As is illu.strated in ~ig. 5 the suction dredgin~ system
comprises a vessel 23, for i.nstance embodied as a
pontoon comprising ballast tanks 24 for controllably
~.ubmerging said vessel a~s is illustrated by the position
of the vessel in relation to the water surface 25. ~t
26 a suction tube 27 is plvotabl.y connected to the
vessel, which suction tube hy mean.s of a piston/cylinder
combination 28 can be moved from a position parallel to
the vessel into a position in which said suction -tube extends
:~.lq-~1.5~3
12
perpendicular]y downwards. The suction tuhe carries
at its bottom end a supporting means 29, whereas the
upper end of the suction tube is through a pipe sectior
30 connected to the suction side of a nump 31, o which
the pressuring side is connected to a pressure pipe
32 running to a location not illustrated in detail,
where the suctioned hottom material is delivered.
Furthermore, the vessel comprises anchoring means such
as a cable 33 running e.g. to an anchoring point on dry
land and a cable 34 running from a winch 35 e.g. to an
anchoring buoy.
As is illustrated in fig. 5 the suction tube 27 is
forced into the undisturhed bottom 17 hy submerging
the vessel over a certain distance, such that the suction
tube and the vessel is supported on the ~ottom by the
underside of the supporting means 29, whereby during
the functioning of the system the ~ottom material
moves according to the arrows 36 and is suctioned through
the open bottom end of the suction tube in and through
the suction tuhe and is passed thereafter thrc~ugh the
pressure conduitO
In fig. 6 several stages are schematically indicated
during the functioning of the system in shallow water,
according to fig. 5. In fig. 6a the vessel 23 has
arrived at its place of destination.
~ ~51~
13
Fig. 6~) illustrated how the suc-tion -tuhe 27 is lowerecl
cn-to the bottom and is supported by said bot-tom, where-
after the suctioning o~ bo~tom material is started
during which procedure the suction -tube27 is gradually
rotated downwards as illustrated in ~ig. ~c ancl forms
thereby an excavation in ~he bottom ma-terial.
In fig. 6d the suction tuhe 27 has reached a downward
extending position in relation to the vessel, so that
for further and deeper suctioning o F bot-tom material
the vessel should ~e submerged as is illustrated in
fi~. 6e.
In fig. 6f the supporting means 29 is forced deeper into
the bottom to create a supporting surface at a deeper
level such that the suctioning o~ bo-ttom ~aterial can
proceed a system supported on the bottom.
As is illustratea in fig. 7 the suction tuhe 37 compxises
an inner tube 38 and an outer tube 39, coaxially
positioned at a distance of each other such that an
annular space 40 between said tubes is formed which
space is closed at the underside of the suction tube by
the ring 41.
In the annular shaped space 40 a numher, e.g. -four
piston/cylinder units ~2 are installed o~ which the piston
rods 43 are connected to the pipe sections 44, which
pipe sections 44 are slidably guided -through OpeninCJS
1~
in the ring 41. ~t their ~ottom ends the pipe sec-tions
44 are connected to the annular supporting mean~ 45,
such that by controlling the piston/cylincler unlts 42
the distance between said supporting means ~5 and the
bottom end of the suction tube 37 coinciding with the rin~
41 can be alteredO
The suction tuhe is, by means of axles 46, pivotably
connected to the vessel.
In the figs. 8 and 9 an embodiment Orc the suction -tube
is illustrated. Said suction tube comprises an outer
tube 47 ancl, coaxially therewith at some distance inwards,
the inner tube ~8, functioning as the real suction tube.
The annular shaped supporting means 49 is connected
through elongated wall sections 50, 51 of the respective
outer and inner tube to said tu~es. In said elongated
wall sections 50, 51 A number of opposed openings
or windows 52, 53 respectively are macle. Openin~s 55
are made in the lower surface 54 of the supportin~
means 49 and through said openings a pr~ssurized fluid
can be sprayed, which fluid is supplied via the annular
shaped space between the inner and outer tube 4~, 49
and between the extension walls 51, 50.
The suction tube in the figs~ 10, ]l and 12 and 13
comprises furthermore an outer tube 57 ancl coaxially at
some distance inwards the inner tuhe 5~ formin-3 the
real suction tuhe, whereas -the annular suppor-tin~ means
59 is connected through the elongated wall 60 to the
outer tube of said suctlon pipe, and .in said elonga-ted
wall 60 a number o:E openings 61 are madeO A slidable
tube section 62 .is installed around said inner -tuhe
which can be made to slide by controlliny the pistonj
cylinder combinations 63 installed in the annular
spaced between the outer tube 57 and the inner tube 58,
with the result that the slidable tube 62 can be
moved from the hicthest position illustrated in Eig. 10
to the lowest posit.ion illustrated in fig. 11 and vice
versa.
The slidable tube 6~ is therehy guided because said
tube is moving within the guiding tube 64 of whlch the
bottom end is attached to the supporting means 59. In
the wall of said guiding tuhe 64 openings 65 are made
opposite the openings 61 in the extension wall 60, but
having an enlarged length ~;m~n~ion in relation to said
openings 61 so that the bottom edges 66 of the openings
65 are situated near the supporting means 59.
If the slidable tube is in its lowest po.sition as is
illustrated in fig. 11 then the slidable tube completely
overlaps the openings 61 in the extension wall 60 a~
some intermediate distance and the openings 65 in the
guiding tube 62 are overlapped for the major part so that
a relatively small part 65a of the openings 65 above
their bottom edg~s 66 is left uncovered. The result
~ ~L5~ 5.~3
16
thereof is that downward c3uidiny channels 67 are ~ormed
between the extension wall 60 of -the outex tube 57 and the
guiding tube 64, which through the openings 61 a-t the
upper side are communicating with the exterior and
through the openings 65a and through the slidable -tuhe
57 are communicating with -the real suction tube 58.
By moving the slidable tube 62 to the lower position in
act the reduced pressure generated in the real suction
tube 58 is tran~mitted to a position near the supporting
means, so that in that case water from the exterior is
suctioned through the channels 67 and ~lows in
downwards direction as is illustrated with arrows 6~,
and these water streams are able to ~luidize and/or
crumble the bottom material around and underneath the
supporting means so that the suction tube can descend
to a lower level.
The suction tube is through the axles 69 pivotably
connected to the vessel.
